function fun1( a:number ,b:number ): number {

    return a + b;

}
fun1( 1, 2 );


function fun2( a:number ,b?:number ): void{
    

}
fun2( 1)


function fun3( a:number= 222 , b:number=111 , c:number ){

}

fun3(  1 , 2  , 3 );



let fun4:(a:number,b:number)=>number = ( a:number , b:number ):number =>{

    return a + b;

}

